Quinoa Protein Isolates Research Articles

Influence of heat denaturation and freezing–lyophilization on physicochemical and functional properties of quinoa protein isolate

AbstractBackgrounds and objectivesQuinoa protein isolate has been shown to confer significant health benefits. However, it is necessary to evaluate the effect of processing on its properties. Therefore, the aim of this work was to evaluate the influence of heat denaturation or freezing followed by lyophilization on the physicochemical and functional properties of the quinoa protein isolate.FindingsFreezing–lyophilization of quinoa protein isolate (QPI‐FL) exhibited a higher foaming capacity and emulsifying capacity at pH 10, and the oil retention capacity was ten times greater that exhibited by the unmodified quinoa protein isolate (QPI), while the particle size and water and oil retention capacity in the modified protein isolate by heat denaturation (QPI‐HD) were twice as compared to QPI. The pH had a significant effect on all physicochemical and functional properties. The flow properties and the micrograph analysis of modified protein isolates revealed greater porosity in comparison with those of the unmodified protein isolate. QPI‐FL showed higher water adsorption capacity at high water activity and a greater displacement in the thermal transitions.ConclusionsIn general, heating did not significantly affect the functional properties of the quinoa protein isolate, while the freezing–lyophilization improved them, which may be of interest in the processes of foods that include in their process the heating or freezing.Significance and noveltyQuinoa protein isolate can be added to different food products with the purpose of improving its composition. However, heating and freezing are two frequent operations in most processes that could affect their properties.

Effect of Transglutaminase Cross-Linking in Protein Isolates from a Mixture of Two Quinoa Varieties with Chitosan on the Physicochemical Properties of Edible Films

The growing demand for minimally processed foods with a long shelf life and environmentally friendly materials has forced industry to develop new technologies for food preservation and handling. The use of edible films has emerged as an alternative solution to this problem, and mixtures of carbohydrates and proteins, may be formulated to improve their properties. The objective of this work was to evaluate the effect of protein cross-linking with transglutaminase (TG) of two varieties of quinoa protein isolate (Chenopodium quinoa) [Willd (QW), and Pasankalla (QP)] on the physicochemical and barrier properties of edible films based on chitosan (CT)-quinoa protein. The evaluated properties were water vapor permeability (WVP), solubility, adsorption, roughness determined by atomic force microscopy, and the interactions among the main film components determined by Raman spectroscopy. The results indicated that TG interacted with lysine of QW and QP. CT:QW (1:5, w/w) showed the lowest solubility (14.02 ± 2.17% w/w). WVP varied with the composition of the mixture. The WVP of CT:quinoa protein ranged from 2.85 to 9.95 × 10−11 g cm Pa−1 cm−2 s−1 without TG, whereas adding TG reduced this range to 2.42–4.69 × 10−11 g cm Pa−1 cm−2 s−1. The addition of TG to CT:QP (1:10, w/w) reduced the film surface roughness from 8.0 ± 0.5 nm to 4.4 ± 0.3 nm. According to the sorption isotherm, the addition of TG to CT-QW films improved their stability [monolayer (Xm) = 0.13 ± 0.02 %]. Films with a higher amount of cross-linking showed the highest improvement in the evaluated physical properties, but interactions among proteins that were catalyzed by TG depended on the protein source and profile.

Production of White, Red and Black Quinoa (Chenopodium quinoa Willd Var. Real) Protein Isolates and Its Hydrolysates in Germinated and Non-Germinated Quinoa Samples and Antioxidant Activity Evaluation.

Red, black and white seeds quinoa were germinated at 28 °C during 24 (G1), 48 and 72 h (G3). Red quinoa presented a higher percentage of germination with a value of 46% of germination at 72 h. Quinoa protein isolate (QPI) was obtained by alkaline extraction (pH 8.0) followed by an isoelectric precipitation (pH 4.5) from white, red and black quinoa seeds, germinated QPI-G1 or QPI-G3 and non-germinated QPI-NG, Chenopodium quinoa Willd var. Real. QPI-G1, QPI-G3 and QPI-NG were subject to a simulated gastric digestion (DG) and in vitro duodenal digestion (DD). The antioxidant activity was evaluated using the 1, 1-diphenyl-2-picryl hydrazyl (DPPH), azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and oxygen radical absorbance capacity (ORAC) methods. Gastric and duodenal digest of QPI-NG and QPI-G1 and QPI-G3 from white, red and black quinoa presented antioxidant activity. QPI-G1-DD of white quinoa presented the highest antioxidant activity with a DPPH value of 167.98 µmoL TE/g of digest, QPI-G1-DD of red quinoa with an ABTS value of 204.86 µmoL TE/g of digest and QPI-G1-DD of black quinoa with an ORAC value of 401.42 µmoL TE/g of digest. QPI-G3-DD of white quinoa presented higher antioxidant activity with a DPPH value of 186.28 µmoL TE/g of sample, QPI-G3-DD of red quinoa with an ABTS value of 144.06 µmoL TE/g of digest and QPI-G3-DD of black quinoa with an ORAC value of 395.14 µmoL TE/g of digest. The inhibition of reactive oxygen species (ROS) production in the zebrafish embryo model (Danio rerio) was evaluated. Protein profiles of QPI from white, red and black from germinated quinoa and non-germinated quinoa were similar with proteins between 10 kDa to 100 kDa with the presence of globulins 11S and 7S and 2S albumins.

Structural prope rties, functional evaluation, and in vitro protein digestibility of black and yellow quinoa (Chenopodium petiolare) protein isolates

ABSTRACTIn this work, the structural and functional properties of proteins from black and yellow quinoa were assessed as well as the in vitro digestibility. Black quinoa flours contained higher amounts of crude fiber and lower amounts of total starch compared to the yellow counterpart. Structurally, electrophoretic SDS-PAGE bands corresponding to 50 kDa 11S globulin, and 55 kDa protein (under non-reducing conditions), and 31–33 kDa (under reducing conditions) were observed in both isolates. Fat absorption and water solubility indexes were comparatively lower in the black quinoa protein isolate. Both isolates showed a good nitrogen solubility index and emulsifying activity. In vitro protein digestibility was similar for both varieties (>95%). The addition of the protein isolates obtained from quinoa flours could be considered as a good alternative to increase the protein content of different foods taking advantage of key functional properties such as nitrogen solubility index and emulsifying activity.

The potential use of modified quinoa protein isolates in cupcakes: physicochemical properties, structure and stability of cupcakes.

The objective of this study was to evaluate the physicochemical, textural, sensory and microbiological stability of cupcakes during storage after the addition of different proportions of quinoa protein isolate modified by heat denaturation (QPI-HD) and freezing-lyophilization (QPI-FL). The cupcakes containing modified quinoa protein exhibited greater firmness and water activity than the control cupcake. The texture profile analysis (TPA) revealed that the cupcakes with modified quinoa protein were statistically different from those with unmodified protein isolate and the control cupcake. Moreover, cupcakes with quinoa protein modified by either heat or freezing had greater acceptance and preference on the part of consumers. In addition to this, these cupcakes showed lesser growth of molds after 10 days of storage; this indicated that the abovementioned additive could extend the shelf life of cupcakes. These results showed that the addition of modified quinoa protein led to cupcakes with better sensory and textural properties and greater stability during storage.

The Influence of Starch and Fibre on In Vitro Protein Digestibility of Dry Fractionated Quinoa Seed (Riobamba Variety)

The in vitro gastric digestibility of the quinoa variety Riobamba was investigated, especially the influence of the quinoa matrix. Dry-fractionated quinoa protein concentrate, which is just milled and sieved, was much better digestible than the same concentrate that was reconstituted from wet fractionated quinoa protein isolate, quinoa starch isolate, and quinoa fibre isolate. In the reconstituted concentrate, the presence of quinoa starch and fibre next to quinoa protein reduces its in vitro gastric digestibility significantly. However, the effect of starch is partially counteracted if the fibre is also present. While the effects of starch and fibre separately can be understood from the decrease of the accessibility for pepsin to hydrolyse proteins, due to the hydrated starch and fibre, we suspect that the synergistic effect of starch and fibre may be due to a relative reduction of the hydration of starch due to the presence of the also strongly hydrating fibre. We concluded that the presence of starch and fibre decreases the protein in vitro gastric digestibility. Therefore, the presence of fibre partially countered the decreased of the protein digestibility of starch. Heating of the matrices to 120 °C generally resulted in much lower digestion rates, due to extensive aggregation of the protein.

Effect of pH and holding time on the characteristics of protein isolates from Chenopodium seeds and study of their amino acid profile and scoring

Alkali extraction and acid precipitation methods were adopted to isolate protein from quinoa and album seeds of variety Chenopodium. Different pH dispersions (3–11) of isolated proteins were prepared and effects of pH and holding time on protein characteristics were evaluated. The pH-10 of extraction medium was found suitable for protein extraction on the basis of yield, purity, solubility and colour having isoelectric pH of 4.5. Yield and purity of protein isolates (PI) of quinoa and album varied from 8.12 to 12.22%; 74.19 to 85.07% and 7.71 to 10.98%; 77.16 to 86.12%, respectively. Overall, pH and time had significant effect on functional properties of PI of both seeds. Quinoa PI had higher emulsifying activity, emulsion stability, water binding capacity and dispersibility, whereas, foaming capacity and stability were higher for album PI. Nutritional indices were 64.20 and 64.58 for quinoa and album PI, respectively, whereas, amino acid scoring (FAO, 2013) indicated, isoleucine, leucine and valine as the limiting amino acids.

Effects of high‐intensity ultrasound pretreatment with different levels of power output on the antioxidant properties of alcalase hydrolyzates from Quinoa (Chenopodium quinoa Willd.) protein isolate

Background and objectivesThe effects of ultrasound pretreatment with different levels of power output (200, 400, and 600 W) on hydrolysis degree of Quinoa protein isolate (QPI) and antioxidant activity of QPI hydrolyzate were studied. The secondary structure, surface hydrophobicity, intrinsic fluorescence, and scanning electron microscopy (SEM) of QPI treated by ultrasound were measured. The untreated QPI and high‐temperature treatment (90°C for 30 min) were used as control.FindingsThe results showed that ultrasound pretreatment at 400 W significantly improved the hydrolysis degree of QPI and antioxidant activity of QPI hydrolyzate. The changes in secondary structure, surface hydrophobicity, and intrinsic fluorescence indicated the unfolding of QPI after ultrasound. The SEM results showed that ultrasound treatment resulted in the deformation of QPI.ConclusionsThe improvement in degree of hydrolysis might be related to the changes in structure induced by ultrasound treatment, which supported more groups for the process of enzymatic hydrolysis.Significance and noveltyThe power output selection of ultrasound pretreatment is essential for improvement of accessibility of QPI to the alcalase and preparation of antioxidant peptides.

Fabrication and Characterization of Quinoa Protein Nanoparticle-Stabilized Food-Grade Pickering Emulsions with Ultrasound Treatment: Interfacial Adsorption/Arrangement Properties.

The natural quinoa protein isolate (QPI) was largely reflected in the nanoparticle form at pH 7.0 (∼401 nm), and the ultrasound at 20 min progressively improved the contact angle (wettability) and surface hydrophobicity of the nanoparticles. Ultrasound process also modified the type of intraparticle interaction, and the internal forces of sonicated particles were largely maintained by both disulfide bonds and hydrophobic interaction forces. In emulsion system, the ultrasound progressively increased the emulsification efficiency of the QPI nanoparticles, particularly at high protein concentration ( c > 1%, w/ v) and higher emulsion stability against coalescence. As compared with the natural QPI-stabilized emulsions, the 20 min sonicated emulsions exhibited higher packing and adsorption at the protein interface. The microstructure of emulsions that occurs is bridging flocculation of droplets at low c (≤1%, w/ v), while the amount of protein particles could be high enough to cover the droplet surface at high c ( >1%, w/ v) with hexagonal array model arrangement. Thus these results illustrated that both natural and sonicated QPI nanoparticles could be performed as effective food-grade stabilizer for Pickering emulsion; however, the sonicated QPI nanoparticles exhibited much better emulsifying and interfacial properties.

Determination of heat-set gelation capacity of a quinoa protein isolate (Chenopodium quinoa) by dynamic oscillatory rheological analysis

This work aimed to study the influence of pH (3.5 and 7.0) and CaCl2 and MgCl2 addition on heat-set gelation of a quinoa protein isolate at 10% and 15% (w/w). The protein isolate obtained was composed mainly of 11S globulin as was observed by electrophoresis and mass spectrometry analysis. Heat-set gelation occurred at both pH values studied. Nevertheless, the gels formed at pH 3.5 were more viscoelastic and denser than those formed at pH 7.0, that was coarser and presented syneresis. The CaCl2 and MgCl2 addition increased the gel strength during rheological analysis at pH 3.5, possibly due to the formation of fiber-like connections in the gel network. At pH 7.0, the divalent salts resulted in weaker gels formed by agglomerates, suggesting a neutralization of the protein surface charges. The differences in quinoa protein gelation were attributed to solubility, and the flexibility of proteins secondary structure at the pH studied.

Denaturation and in Vitro Gastric Digestion of Heat-Treated Quinoa Protein Isolates Obtained at Various Extraction pH.

The aim of this study was to determine the influence of heat processing on denaturation and digestibility properties of protein isolates obtained from sweet quinoa (Chenopodium quinoa Willd) at various extraction pH values (8, 9, 10 and 11). Pretreatment of suspensions of protein isolates at 60, 90 and 120 °C for 30 min led to protein denaturation and aggregation, which was enhanced at higher treatment temperatures. The in vitro gastric digestibility measured during 6 h was lower for protein extracts pre-treated at 90 and 120 °C compared to 60 °C. The digestibility decreased with increasing extraction pH, which could be ascribed to protein aggregation. Protein digestibility of the quinoa protein isolates was higher compared to wholemeal quinoa flour. We conclude that an interactive effect of processing temperature and extraction pH on in vitro gastric digestibility of quinoa protein isolates obtained at various extraction pH is observed. This gives a first indication of how the nutritional value of quinoa protein could be influenced by heat processing, protein extraction conditions and other grain components.

Effect of extraction pH on heat-induced aggregation, gelation and microstructure of protein isolate from quinoa (Chenopodium quinoa Willd)

The aim of this study was to determine the influence of extraction pH on heat-induced aggregation, gelation and microstructure of suspensions of protein isolates extracted from quinoa (Chenopodium quinoa Willd). Quinoa seed protein was extracted by alkaline treatment at various pH values (pH 8 (E8), 9 (E9), 10 (E10) and 11 (E11)), followed by acid precipitation. The obtained protein isolates were freeze dried. The protein isolates E8 and E9 resulted in a lower protein yield as well as less protein denaturation. These isolates also had a higher protein purity, more protein bands at higher molecular weights, and a higher protein solubility in the pH range of 3–4.5, compared to the isolates E10 and E11. Heating the 10%w/w protein isolate suspensions E8 and E9 led to increased aggregation, and semi-solid gels with a dense microstructure were formed. The isolate suspensions E10 and E11, on the other hand, aggregated less, did not form self-supporting gels and had loose particle arrangements. We conclude that extraction pH plays an important role in determining the functionality of quinoa protein isolates.

Physicochemical and Functional Characterization of Protein Isolated from Different Quinoa Varieties (Chenopodium quinoa Willd.)

The objectives of this work were to investigate the nutritional and physicochemical characteristics as well as the functional properties of quinoa protein isolates (QPI) from different varieties, and to determine their potential use of such protein isolates in food products. Proteins were isolated by isoelectric precipitation at pH 5 from quinoa flour, and the QPI had a protein percentage of over 85%. The comparison of the flours and QPI electrophoretic profiles indicated that the extraction method allowed isolating practically all proteins of each variety. All the varieties analyzed had high lysine content, compared with cereals, and the essential amino acid content of Bolivian varieties was higher than varieties from Peru. The pH value affected the solubility and foaming capacity, and the magnitude of effects depended on the variety. Cluster analysis showed a strong influence of variety source and amino acid composition on protein physicochemical and functional properties; samples from Bolivia (cluster 2) were characterized as having the highest thermal stability, oil binding capacity, and water binding capacity at acid pH; samples from Peru (cluster 1) had the highest water binding capacity at basic pH and foaming capacity at pH 5. QPI presented a potential as an alternative vegetable protein for food application, in particular for vegetarian and vegan diets.

Physicochemical and functional properties of quinoa protein isolate

This study was focused on the optimum conditions for preparing the protein isolate of quinoa seeds and investigates the physicochemical and functional properties of the isolated protein to assess the potential use of quinoa protein isolate in food applications and manufacturing. The protein isolate of quinoa was obtained by protein solubility at alkaline pH value (10), followed by precipitation at an acidic pH value (4.5). SDS–PAGE showed protein bands with 55KDa corresponding to globulin and 31–33KDa corresponding to chenoprotein in all extraction pHs. Quinoa protein had reasonable concentrations of essential amino acids (except tryptophan) with a high level of lysine (17.13%). A sharp minimum solubility was observed at the pH value (4.5), and the maximum value was observed at the alkaline pH value (10) (P>0.05). Quinoa protein showed a high In Vitro digestibility (78.37±1.08%). The quinoa protein showed water absorption (3.94±0.06ml/g) and (1.88±0.02ml/g) oil absorption. The foaming capacity of quinoa protein isolate was (69.28±9.39% in average) and the foaming capacity was increased with the increase in the protein concentration. Quinoa protein isolate registered 54.54±15.31% foam stability after 60min. Emulsion ability index was ranged from 1.24±0.05m2/g for 0.1% protein suspension to 3.38±0.31m2/g for 3% protein suspension with average 2.10±0.99m2/g. The average of emulsion stability index was (38.43±7.22min). Quinoa protein isolate is a promising and impressive nutritive source, which is leading to candidate it as a food supplement and functional food but still needs more advanced research to improve and proof its functional properties to be convenient for using in food processing and additives.

Quinoa (Chenopodium quinoa Willd.) protein hydrolysates with in vitro dipeptidyl peptidase IV (DPP-IV) inhibitory and antioxidant properties

The potential of quinoa to act as a source of dipeptidyl peptidase IV (DPP-IV) inhibitory and antioxidant peptides was studied. A quinoa protein isolate (QPI) with a purity of 40.73 ± 0.90% was prepared. The QPI was hydrolysed at 50 °C for 3 h with two enzyme preparations: papain (P) and a microbial papain-like enzyme (PL) to yield quinoa protein hydrolysates (QPHs). The hydrolysates were evaluated for their DPP-IV inhibitory and oxygen radical absorbance capacity (ORAC) activities. Protein hydrolysis was observed in the QPI control, possibly due to the activity of quinoa endogenous proteinases. The QPI control had significantly higher DPP-IV half maximal inhibitory concentrations (IC50) and lower ORAC values than QPH-P and QPH-PL (P < 0.05). Both QPH-P and QPH-PL had similar DPP-IV IC50 and ORAC values. QPH-P had a DPP-IV IC50 value of 0.88 ± 0.05 mg mL−1 and an ORAC activity of 501.60 ± 77.34 μmol Trolox equivalent (T.E.) g−1. To our understanding, this is the first study demonstrating the in vitro DPP-IV inhibitory properties of quinoa protein hydrolysates. QPHs may have potential as functional ingredients with serum glucose lowering properties.

Modifying the Cold Gelation Properties of Quinoa Protein Isolate: Influence of Heat-Denaturation pH in the Alkaline Range.

Heat-denaturation of quinoa protein isolate (QPI) at alkali pH and its influence on the physicochemical and cold gelation properties was investigated. Heating QPI at pH 8.5 led to increased surface hydrophobicity and decreases in free and bound sulfhydryl group contents. Heating at pH 10.5 caused a lesser degree of changes in sulfhydryl groups and surface hydrophobicity, and the resulting solutions showed drastically increased solubility. SDS PAGE revealed the presence of large aggregates only in the sample heated at pH 8.5, suggesting that any aggregates present in the sample heated at pH 10.5 were non-covalently bound and disintegrated in the presence of SDS. Reducing conditions partially dissolved the aggregates in the pH 8.5 heated sample indicating the occurrence of disulphide bonding, but caused no major alterations in the separation pattern of the pH 10.5 heated sample. Denaturation pH influenced the cold gelation properties greatly. Solutions heated at pH 8.5 formed a coarse coagulum with maximum G' of 5 Pa. Heat-denaturation at 10.5 enabled the proteins to form a finer and regularly structured gel with a maximum G' of 1140 Pa. Particle size analysis showed that the pH 10.5 heated sample contained a higher level of very small particles (0.1-2 μm), and these readily aggregated into large particles (30-200 μm) when pH was lowered to 5.5. Differences in the nature of aggregates formed during heating may explain the large variation in gelation properties.

Study of Some Physicochemical and Functional Properties of Quinoa (Chenopodium Quinoa Willd) Protein Isolates

The amino acid composition and the physicochemical and functional properties of quinoa protein isolates were evaluated. Protein isolates were prepared from quinoa seed by alkaline solubilization (at pH 9, called Q9, and at pH 11, called Q11) followed by isoelectric precipitation and spray drying. Q9 and Q11 had high levels of essential amino acids, with high levels of lysine. Both isolates showed similar patterns in native/SDS-PAGE and SEM. The pH effect on fluorescence measurements showed decreasing fluorescence intensity and a shift in the maximum of emission of both isolates. Q9 showed an endotherm with a denaturation temperature of 98.1 degrees C and a denaturation enthalpy of 12.7 J/g, while Q11 showed no endotherm. The protein solubility of Q11 was lower than that of Q9 at pH above 5.0 but similar at the pH range 3.0-4.0. The water holding capacity (WHC) was similar in both isolates and was not affected by pH. The water imbibing capacity (WIC) was double for Q11 (3.5 mL of water/g isolate). Analysis of DSC, fluorescence, and solubility data suggests that there is apparently denaturation due to pH. Some differences were found that could be attributed to the extreme pH treatments in protein isolates and the nature of quinoa proteins. Q9 and Q11 can be used as a valuable source of nutrition for infants and children. Q9 may be used as an ingredient in nutritive beverages, and Q11 may be used as an ingredient in sauces, sausages, and soups.